Process for obtaining tanning material from cellulose waste sulphite lyes



Patented Jan. 9, 1923.

UNITED STATES PATENT OFF-ICE.

ADOLF Roman, or sru'r'ream', GERMANY.

PROCESS FOR OBTAINING TANNING No Drawing.

1919, Jan. 31, 1919; Norway, Feb. 11, 1919),

of which the following is a specification.

It has been suggested, for the purpose of obtaining tannin substances from waste sulphite cellulose yes, to neutralize the lye with lime and after separation of the calcium sulphite precipitated to mix with metal sulphates such as for instance alum, for the purpose of obtaining tannates of metals with separation of gypsum. Tanning lyes thus obtained, always contain lime which is undesir ble for tanning purposes, in the form 01' tannates of lime, or of gypsum. Another suggestion was to pass sulphite lye neutralized with milk of lime, through an osmotic apparatus, and for the purpose of further conversion into a tanning substance, to free the non-diffusing portion entirely or partly from lime by means of sulphuric acid. But in this case also it is impossible to obtain a solution free from lime. It has been further suggested to free sulphite lyes from lime by means of soda, and to use the solutions which are then preferably mixed with alum, for tanning, but with the addition before, during or after,the tanning process, of diluted acid for the purpose of neutralizing the alkalies released during the tanning which spoiled the colour of the leather on the surface and in section. Such tanning lyes are practically useless as they contain-sulphurous acid which is very injurious for tanning. For the purpose of obtaining tanning liquors which are free from lime and sulphurous acid, it has been sug gested to free the lye from the chief quantity of sulphurous acid and calcium sulphite by heating or treatment in vacuo, to convert the remainin free and bound sulphurous acid into su phuric acid by means of ozone, and finally to cause it to react with carbonate of barium.

According to the present process it is possible to obtain in a most simple technical Application filed April 9,

MATERIAL rnom CELLULOSE wasrn SULPHITE LYES.

1921. Serial No. 460,147.

manner tanning substances with excellent tanning properties, free from injuriousingredlents, more particularly from sulphurous acid and lime by converting the acids contained in the waste lyes, such as sulphurous acid, sulpholignic acid, etc, or the r acid salts, into neutral salts, by means of an alkaline calcium compound such as milk of lime, carbonate oflime or the like, owing to which all sulphurous acid is precipitated in the form of neutral sulphite of lime, whereupon the solution is freed from the substances Precipitated, and mixed with suitable alkali compounds, for instance alkali. carbonate or alkali silicate, for the purpose of converting the lignine-sulfonates of lime into lignine-sulfonates of an alkali metal, with quantitative precipitation of the lime. The lye thus obtalned which contains sulpho-lignic acid in the form of a neutral alkali salt, has no tanning effect; the latter is only obtained "when the alkali salt is mixed with a strong acid such as for instance hydrochloric acid or sulphuric acid. It has been found that the quantity of acid added must not be less than half the quantity theoretically required for converting the lignine alkali metal sulfonate into the free sulfonic acid, and not'materially more'than theoretically required for complete converslon.

An advantageous method of carrying out the invention consists in subjecting the lye neutralized with milk of lime or carbonate of lime, after separating the substances thus precipitated, to fermentation. It is preferable in that case to pass the lye through a closed system of fermentation vessels charged with yeast fixed on a carrier. The liquid thus freed from sugar, is then further treated, in the manner already described, with alkali compounds and, after separation of the carbonate of lime precipitated, condensed by evaporation and mixed with acid. By fermenting the sugar, not only alcohol is obtained, but-the tannin extract is improved by the removal of the sugar which is a non-tanning sub-stance.

Another modification of the invention consists in acting on the li'gnine-sulfonates of alkali metals not with hydrochloric acidor sulphuric acid, but in using in their place acid-reacting salts of metals such as are utilized for the purpose of mineral tanning, for instance aluminium chloride,'ferric chloride or chromium-chloride. Compound tanning substances with s ecially favourable properties are thus obtained. They quickly and completely penetrate into the animal hide both in concentrated and in diluted solution, so that in both cases excellent and fully tanned leather is obtained.

A specially remarkable behaviour is that of ferric oxide salt. As is well known, in iron tanning the effective ferric oxide salts cannot be used directly for tanning, as they do not penetrate into the hide. In order to ensure tanning right through it was hitherto necessary to treat the unhaired skins with non-tanning ferrous oxide salts which have a better diffusion property and to convert them on the hide into tanning ferric oxide salts by oxidation. It is therefore surprising that ferric oxide .salt of sulpho-lignic acld can be successfully used directly for tanning.

Exam le. The waste sulphite lye is supersaturate with milk of lime or with chalk. Qther disturbing impurities, more particularly resin-like substances, are precipitated at the same time. The remaining solution is thereupon treated with sodium carbonate, and to the liquid separated from the precipitate, is added half of the amount of hydro chloric acid or of one of the above mentioned metal chlorides, theoretically required for binding the alkali metal of the alkali metal li nine-sulfonates. The amount of acid or of the acid-reacting metal salt can be determined in a very simple manner, as the quantity of soda consumed for the conversion of lignine-sulfonate compound of lime, gives directly the measure of the acidaddition. By evaporating the solutions prepared in accordance with the present process, highly efficient tanning extracts are obtained,which in addition to the already -mentioned advantages of the absence of injurious and undesired substanoes, have also the great advantage of always being of uniform eflicacy, a very important property for properly regulating tanyard working. which is absent in most extracts obtained from sulphite lyes.

A special advantage is that formation o-f free mineral acids is avoided in any case.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I hereby declare that what I claim is 1. A process for obtaining tanning substances from waste sulfite cellulose lye consisting in first subjecting the lye to the action of an alkaline calcium compound for the purpose of precipitating all of the sul-,

furous acid, then removing the precipitate and subjecting the remaining solution to the action of alkali compounds capable of precipitating the calcium. combined with the sulfo-lignic acids thereby converting the lignine compounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfonates with a compound of acid character.

2. A process for obtainin tanning substances from waste sulfite ce lulose lye consisting in first subjecting the lye to the action of an alkaline calcium compound for the purpose of precipitating all of the sulfurous acid, then. removing the precipitate and subjecting the remaining solution to the action of alkali compounds capable of precipitating the calcium combined with the sulfodignic acids thereby convertin the lignine coinpounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfon-ates with a compound of acid character whereby the quantity of the latter is less than the quantity required for combining with all of the alkali metal of the lignine-sulfonate.

3. A process for obtaining tanning substances from waste sulfite cellulose lye consisting in first subjecting the lye to the acation of an alkaline calcium compound for the purpose of precipitating all of the sulfurous acid, then removing the precipitate and subjecting the remainin solution to the action of alkali compounds capable of precipitating the calcium combined with the sulfo-lignic acids thereby converting the lignine compounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfonates with a compound of acid character whereby the quantity of the latter is about one half of the quantit required for combining with all of the alka i metal of the lignine-sulfonate.

4. A process for obtaining tanning substances from waste sulfite cellulose lye conslsting in first subjecting the lye to the action of an alkali calcium compound for the purpose of precipitating all of the sulfurous acid, then removing the precipitate and subjecting the remaining solution to fermentation, then treatin it with alkali compounds capable of precipitating the calcium combined with the sulfo-lignic acids thereby converting the lignine compounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfonates with a compound of acid character.

5. A process for obtaining tanning substances from waste sulfite cellulose lye consisting in first subjecting the lye to the action of an alkaline calcium compound for the purpose of precipitating all of the sulfurous acid, then removing the precipitate and subjecting the remaining solution to fermentation, then treating it with alkali compounds capable of prccipitating'the calcium combined with the sulfo-lignic acids thereby converting the lignine compounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfonates with a salt of a metal suitable for mineral tanning.

- cium combined with the sulfo-lignic acids thereby converting the lignine compounds into alkali metal lignine sulfonates and lastly treating said alkali metal lignine sulfonates with a salt of a metal suitable for mineral tanning in a quantity insufficient to convert all of the alkali metal lignine sulfonate into the metal lignine sulfonate.

7. A process for obtaining a tanning substance from waste sulfite liquor 'conslsting in first adding to the liquor calcium carbonate to precipitate all of the sulfurous acid, then removing the precipitate and subjecting the remaining solution to the action of alkali metal carbonate, thereby converting the lignine compounds into alkali metal lignine-sulfonates and then adding hydrochloric acid in a quantity insufficient to combine with all of the alkali metal of the lignine sulfonate.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

' DR. ADOLF ROMER.

Witnesses:

WILHELM STKHLE, AUGUST FREY. 

